Thus Luther and Zwingle had insensibly separated from each other. It is probable however that peace might have subsisted longer between them, if the turbulent Carlstadt, who kept passing to and fro between Switzerland and Germany, had not inflamed these contrary opinions. [Sidenote: BEGINNING OF THE CONTROVERSY.] A step taken with a view to maintain peace led to the explosion. The council of Zurich, desirous of preventing all controversy, forbade the sale of Carlstadt's works. Zwingle, who disapproved of his violence, and blamed his mystical and obscure expressions,[622] thought himself now called upon to defend his doctrine, both in the pulpit and before the council; and shortly after wrote a letter to Albert, pastor of Reutlingen, in which he said: "Whether or not Christ speaks of the sacrament in the sixth chapter of St. John, it is very evident that he there inculcates a manner of eating his flesh and drinking his blood, in which there is nothing corporeal."[623] He then proceeded to prove that the Lord's Supper, by reminding the faithful, according to Christ's intention, of his body which was broken for them, procured for them that spiritual eating which alone is truly salutary. [622] Quod morosior est (Carlstadius) in cæremoniis non ferendis, non admodum probo. Zw. Epp. p. 369. [623] A manducatione cibi, qui ventrem implet, transiit ad verbi manducationem, quam cibum vocat cœlestem, qui mundum vivificet. Zw. Opp. iii. 573. Yet Zwingle shrunk from a rupture with Luther; he trembled at the thought that these unhappy disputes might tear in pieces that new society which was then forming in the midst of fallen Christendom. But it was not so with Luther. He did not hesitate to class Zwingle with those enthusiasts against whom he had already broken so many lances. He did not reflect that if the images had been taken down at Zurich, it was done legally and by order of the public authority. Accustomed to the forms of the German principalities, he knew but little of the proceedings of the Swiss republics; and he inveighed against the grave divines of Helvetia, as he had done against the Munzers and Carlstadts. Luther having published his _Treatise against the Celestial Prophets_, Zwingle no longer hesitated, and at nearly the same time he gave to the world his _Letter to Albert_, and his _Commentary on True and False Religion_, dedicated to Francis I. In this last he said: "Since Christ, in the sixth chapter of St. John, ascribes to faith the power of imparting eternal life, and of uniting the believer to Him in the closest union, what need have we of more? Why should He afterwards have ascribed this virtue to His flesh, whilst He himself declares that His flesh profiteth nothing? The flesh of Christ, so far as it suffered death for us, is of incalculable utility, for it saves us from perdition; so far as it is eaten by us, it is of no use whatever."